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Forget blowing up a doomsday asteroid with nuclear bombs. We probably won't even see it coming.

Via the European Space Agency, an artist's rendering of Apophis.

David Ewalt reports on asteroid 99942 Apophis, a hunk of space rock discovered back in 2004 that astronomers said had "a small chance" of collision "with the Earth in the year 2029, causing an explosion equivalent to 1480 megatons of TNT–nearly 30 times larger than the biggest hydrogen bomb ever detonated."

We had a "close pass" with the asteroid yesterday---veering around 9 million miles close to our planet.

According to Ewalt, scientists are now claiming the asteroid is about 20% bigger than they first thought, and even though it's still not likely that Apophis will collide with our planet, if it did the impact would be even more dire. The near pass should help scientists project collision likelihood well into the future.

Apophis is what we refer to as a Near Earth Object (or NEO.) NEOs are "small objects in the solar system (asteroids and short-period comets) with orbits that regularly bring them close to the Earth and which, therefore, are capable someday of striking our planet," according to NASA.

What's actually frightening about NEOs is that there are actually lots and lots of them that we don't even know about. 99942 Apophis is an outlier not because it could theoretically hit Earth, but because we know about it in the first place. Scientists tagged it as a possible 2029 collision. That's quite a few years to formulate some sort of defense.

So how much warning will we really have if an asteroid is about to hit Earth? The answer is pretty grim.

"With so many of even the larger NEOs remaining undiscovered, the most likely warning today would be zero," NASA informs us. We would see nothing at all until suddenly, just as the impact occurred, we noticed a "flash of light and the shaking of the ground as it hit." Then poof.

Compared to the sudden, unanticipated impact, "if the current surveys actually discover a NEO on a collision course, we would expect many decades of warning. Any NEO that is going to hit the Earth will swing near our planet many times before it hits, and it should be discovered by comprehensive sky searches like Spaceguard. In almost all cases, we will either have a long lead time or none at all."

Apophis obviously falls into the "many decades" camp, though it's unlikely it will hit Earth in our lifetime.

The more likely scenario? I'll be typing a post like this one when suddenly "a flash of light and the shaking of the ground" and then...well you get the picture.

Not much fanfare, I'll admit, but life is usually stranger---and more abrupt---than the movies.